valve clearance changed

[cloudchaser]

The engine developed a "lope", lost power, and started smoking while climbing a hill. I first thought it was the injectors, but decided to test compression. All in the 300 + range. Took off the valve cover to check valve clearance. Some valves had very wide clearance. I had set them 2 years ago. The locknuts were tight. The valve with the widest clearance had over 1/4" - had to be turn in the adjustment screw until the top end is deep into the locknut to get the right clearance. The end looks ok; the cam rocker roller seems ok, as does the camshaft. I cannot guess what could be wrong. Any suggestions?

[Growlerbearnz]

That's an odd one.

The rockers are quite weak, they're designed to break if the pistons should hit the valves. It's not unknown for rockers to suddenly break for no reason- perhaps yours are on the way out? But it would be strange for more than one to start doing that.

[cloudchaser]

Thanks Growlerbernz. You got me checking the rocker arms and led to removing the shaft they are operating on. The valve that I was most concerned about had a failed bearing on the roller. This was the front exhaust valve. The other exhaust roller bearings are loose. My Delica has just 122K on it - seems very soon for a failed bearing. does anyone have any ideas why this has happened? I phoned my local dealer who said he may have some used rockers, but mostly intake. My intake rockers seem to be OK.